Neutron Material Science

Associate Professor

MORI, Kazuhiro e-mail: kmori<atmark>

Assistant Professor

ONODERA, Yohei e-mail: y-onodera<atmark>

* replace <atmark> with ＠rri.kyoto-u.ac.jp

The neutron is a powerful probe for the study of condensed matter (disordered [amorphous, glass], crystalline, non-equilibrium, and nanocomposite materials) in the world around us. Neutron scattering gives detailed information about atomic level structure and dynamics, that is, where atoms are and how they are moving. Neutrons used in our experiments have wavelengths that are similar to atomic spacing, allowing the structures of materials to be studied by diffraction on scales from atomic dimensions to macromolecular scales. At the same time, the neutrons have energies that are similar to those of atomic processes like molecular transitions, rotations, vibrations, and lattice modes.

Recently, the subject of our group is focused on getting structural information of functional materials: rechargeable batteries, hydrogen storage materials, air-separating membranes, cement clinkers, etc. In particular, three dimensional locations of light atoms, lithium and hydrogen, in the condensed matter can be precisely determined by the Rietveld and pair distribution function (PDF) analyses, and the reverse Monte Carlo (RMC) modeling based on neutron and X-ray diffraction data (see Fig. 1). Moreover, from a viewpoint of dynamics of water, the hydration reaction in cement paste can be observed using the quasi-elastic neutron scattering (QENS) technique, by taking advantage of the difference in diffusion constant between free and bound water (see Fig. 2).

Fig. 1. Three-dimensional structures of (Li2S)70(P2S5)30 glass (left) and Li7P3S11 metastable crystal (right), which are lithium-ion conductors as promising candidates of solid electrolytes in all-solid-state lithium-ion batteries. The electrical conductivity of Li7P3S11metastable crystal is approximately one order of magnitude larger than that of (Li2S)70(P2S5)30 glass. In the predicted conduction pathways of lithium ions, the orange and blue regions correspond to the “stable” and “metastable” regions for the lithium ions.

Fig. 2. Time evolution of the quasi-elastic neutron scattering (QENS) spectrum for Low Heat Portland Cement (LHPC) (left) and time dependence of the compressive strength for mortar based on the LHPC (right).